ACT4910QW
Rev 1.0, 15-Sept-2017
4. The FB pin should be Kelvin connected to the
output capacitor through the shortest possible
route, while keeping sufficient distance from
switching node to prevent noise injection. The
IC regulates the output voltage to this Kelvin
connection.
PC board layout guidance
Proper parts placement and PCB layout are critical to
the operation of switching power supplies. Follow the
following layout guidelines when designing the
ACT4910 PCB. Refer to the Active-Semi ACT4910
Evaluation Kits for layout examples
5. Connect the PGND and VSS ground pins must
be electrically connected together. The VSS
ground plane should be isolated from the rest
of the PCB power ground.
1. Place the buck input capacitors as close as
possible to the IC. Connect the input capacitors
directly between STR and PGND pins on the
top layer. Routing these traces on the top layer
eliminates the need for vias.
6. Remember that all open drain outputs need
pull-up resistors.
2. Minimize the switch node trace length between
the SW pin and the inductor. Optimal switch
node routing is to run the trace between the in-
put capacitor’s pads. Using 1206 or larger sized
input capacitors is recommended. Avoid routing
sensitive analog signals near these high fre-
quency, high dV/dt traces.
7. Connect the exposed pad directly to the top
layer ground plane. Connect the top layer
ground plane to both internal ground planes
and the PCB backside ground plane with ther-
mal vias. Provide ground plane routing on mul-
tiple layers to allow the IC’s heat to flow into the
PCB and then spread radially from the IC. Avoid
cutting the ground planes or adding vias that re-
strict the radial flow of heat.
3. The Buck output capacitors should be placed
by the inductor and connected directly to the in-
ductor and ground plane with short and wide
traces. The output capacitor ground should
make a short connection to the input capacitor
ground. If required, use multiple vias.
Innovative PowerTM
ActiveSwitcherTM is a trademark of Active-Semi
www.active-semi.com
Copyright © 2017 Active-Semi, Inc.
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